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This paper introduces a sensitivity-enhanced fault detection algorithm, termed the Fault Diagnosis and Amplifying (FDnA) method, designed to amplify fault signals in induction motors with broken rotor bars. The FDnA algorithm employs a cascaded state observer structure, integrating stator flux linkage and stator current observers based on an analytical model of an induction motor. By multiplying the output signals of these observers, the algorithm significantly enhances the sensitivity of fault detection. The FDnA method is robust against external environmental conditions and excels in accurately detecting broken rotor bar faults. Additionally, it offers a cost-effective and retrofittable solution by replacing traditional sensors and interfacing circuits with state observers, eliminating the need for additional hardware. Comprehensive validation through simulations and rapid control prototyping highlights the superior fault detection sensitivity of the FDnA method compared to conventional approaches, establishing it as a reliable and efficient advancement in fault detection for induction motors.

A permanent magnet synchronous motor (PMSM) drive has been widely used for various industrial applications such as electric vehicles (EVs) and home appliances due to its attractive features such as high power/torque density and high efficiency. While a PMSM has various attractive features, it also includes some drawbacks such as parameter sensitivity with respect to operating conditions of PMSMs. For example, permanent magnet (PM) flux linkage of an IPMSM is decreased as magnet temperature of in a rotor of PMSM increases. As known, a characteristic current of a PMSM is determined by its PM flux linkage and an operating region and operating characteristic are affected by the characteristic current. In this paper, a control algorithm is proposed for a PMSM drive to adjust its operating region actively by reflecting PM variations in real time. PM flux linkage of a PMSM is estimated through a stator flux linkage observer in real time and the estimated PM flux linkage is applied to the active operating region adjustment (AORA) algorithm for more effective utilization of an IPMSM drive operation. The proposed AORA algorithm for a PMSM drive is implemented and verified experimentally in this paper.

This study attempted to provide the basic data for developing a system to identify the role of medical technologists and ensure an efficient response for quick and accurate diagnostic tests in the COVID-19 era. The research method involved using focus group interviews for a survey and analysis of 15 medical institutions. Eleven sample collection institutions, 10.4 medical technologists, 2.1 minutes of collection time, 5.4 hours of test time, 9,670 tests, 6.2 member test workforce size, and 7 screening center operating institutions were surveyed. The results of the focus group interview analysis revealed that there were no standardized guidelines covering working hours, area, and environment to protect sample collectors and testers in relation to the COVID-19 tests. Also, legal protection measures were insufficient in the event of accidental infections and there were no personnel regulations related to COVID-19. In addition, the professional training of sample collectors and molecular diagnostic testers was required for reliable COVID-19 testing. In conclusion, it is necessary to provide professional education through special test short-term training institutions to cope with emergency infectious diseases such as COVID-19. Legal systems should be put in place to protect the workforce and ensure stability.

This paper presents a state-of-the-art review in modeling approach of hardware in the loop simulation (HILS) realization of electric machine drives using commercial real time machines. HILS implementation using digital signal processors (DSPs) and field programmable gate array (FPGA) for electric machine drives has been investigated but those methods have drawbacks such as complexity in development and verification. Among various HILS implementation approaches, more efficient development and verification for electric machine drives can be achieved through use of commercial real time machines. As well as implementation of the HILS, accurate modeling of a control target system plays an important role. Therefore, modeling trend in electric machine drives for HILS implementation is needed to be reviewed. This paper provides a background of HILS and commercially available real time machines and characteristics of each real time machine are introduced. Also, recent trends and progress of permanent magnet synchronous machines (PMSMs) modeling are presented for providing more accurate HILS implementation approaches in this paper.

This paper presents a stationary reference frame grid current control algorithm for a grid-connected inverter (GCI) to improve command tracking performance and resilience in response to disturbances, i.e., a grid voltage incident in a GCI current control system. In the proposed algorithm, disturbance rejection is applied to reduce the overcurrent at the GCI in response to a grid fault. Disturbances to the GCI current control system are estimated using a grid current observer, and the estimate applied to the grid current controller to activate the disturbance rejection. The stationary reference frame current of a GCI system is also controlled to avoid cross-coupling issues at a synchronous reference frame model, reference transformation and dependency to phase locked loop (PLL) performance. However, the phase lead or lag and steady-state response error, which are drawbacks of AC signal control based on stationary reference frame proportional-integral (PI) controller, must be eliminated in order to secure competition with the synchronous reference PI (SRFPI) controller that was mainly used in the GCI system. Hence, to compensate for command tracking the AC current, such as steady-state response error and phase lead or lag, command feedforward control is applied in the proposed control system. The theory behind the proposed GCI current control algorithm is analyzed, and the proposed algorithm is tested via simulation and experimentation.

In a single-phase grid-tied inverter, the direct current (DC) offset error included in the measured grid side phase current has various causes, such as a non-ideal current sensor, unbalanced power supply of an operational amplifier, and nonlinear features of analog components in interface circuits, etc. If the DC offset error is included in the measured current, it causes the secondary harmonic of fundamental frequency and the DC component in grid phase current which result in degradation of inverter performance. In this paper, a theoretical detection method of the secondary harmonic of the fundamental frequency and a DC component in grid phase current for a proportional-resonant (PR) current control system is introduced. Based on the detection method, an algorithm for compensating DC offset error is also presented for single-phase grid-tied inverters. Simulation results and experimental verification of the DC offset error compensation algorithm are shown in this paper.

This paper presents a stability analysis and dynamic characteristics investigation of deadbeat-direct torque and flux control (DB-DTFC) of interior permanent magnet synchronous motor (IPMSM) drives with respect to machine parameter variations. Since a DB-DTFC algorithm is developed based on a machine model and parameters, stability with respect to machine parameter variations should be evaluated. Among stability evaluation methods, an eigenvalue (EV) migration is used in this paper because both the stability and dynamic characteristics of a system can be investigated through EV migration. Since an IPMSM drive system is nonlinear, EV migration cannot be directly applied. Therefore, operating point models of DB-DTFC and CVC (current vector control) IPMSM drives are derived to obtain linearized models and to implement EV migration in this paper. Along with DB-DTFC, current vector control (CVC), one of the widely used control algorithms for motor drives, is applied and evaluated at the same operating conditions for performance comparison. For practical analysis, the US06 supplemental federal test procedure (SFTP), one of the dynamic automotive driving cycles, is transformed into torque and speed trajectories and the trajectories are used to investigate the EV migration of DB-DTFC and CVC IPMSM drives. In this paper, the stability and dynamic characteristics of DB-DTFC and CVC IPMSM drives are compared and evaluated through EV migrations with respect to machine parameter variations in simulation and experiment.

This paper presents a torque error compensation algorithm for a surface mounted permanent magnet synchronous machine (SPMSM) through real time permanent magnet (PM) flux linkage estimation at various temperature conditions from medium to rated speed. As known, the PM flux linkage in SPMSMs varies with the thermal conditions. Since a maximum torque per ampere look up table, a control method used for copper loss minimization, is developed based on estimated PM flux linkage, variation of PM flux linkage results in undesired torque development of SPMSM drives. In this paper, PM flux linkage is estimated through a stator flux linkage observer and the torque error is compensated in real time using the estimated PM flux linkage. In this paper, the proposed torque error compensation algorithm is verified in simulation and experiment.

In this paper, impedance modeling of a DC microgrid system consisting of a source and load converter, including an input filter, is performed. Impedance-based modeling has been used to derive mathematical models of the output impedance of the source converter and the input impedance of the load converter. The correlation between the converter interaction and system stability is analyzed based on the mathematical model. An impedance-based stability analysis is used to determine the system stability by analyzing the interactions among the converters in the DC microgrid system. Middlebrook's stability criterion, which uses the impedance transfer function, is applied to determine system stability. Moreover, in this paper, a stability enhancement control algorithm is proposed to resolve the system instabilities resulting from interaction among the converters and the distortion caused by the harmonics emanating from the AC input. The proposed stability enhancement control algorithm consists of a feed-forward type virtual impedance (VI) and a proportional-resonant (PR) controller. The validity of the proposed method is demonstrated by the results of the response characteristics in the frequency domain, and the effectiveness of the proposed control algorithm is verified via simulations and prototype experimental models.

Background. Bacteremia is a major nosocomial infection that frequently occurs in trauma patients, increasing morbidity and mortality. The aim of this study was to identify risk factors and to describe epidemiological patterns for early onset (EOB) and late onset (LOB) bacteremia after trauma. Methods. We retrospectively reviewed medical records of all trauma patients admitted to the surgical intensive care unit and general ward between January 2011 and December 2015. The information was collected for each patient and recorded in a computer database: early onset bacteremia (EOB) was defined as when onset occurred within 7 days after trauma, and late onset bacteremia (LOB) was defined as when onset occurred after 7 days from trauma. Results. Thirty-four patients of 859 (4%) developed bacteremia during their hospital stay: 4 (11.8%) developed EOB, 26 (76.4%) LOB, and 4 (11.8%) patients developed both of them. Sixty events of bacteremia happened to these patients: 9 (15.0%) EOB and 51 (85.0%) LOB. Gram-positive cocci were isolated more frequently than Gram-negative bacilli in both groups. Gram-positive cocci were more frequently isolated in EOB than in LOB; otherwise, there was no statistical significance (77.8% vs. 64.7%, p=0.683). Central line-associated blood stream infection (CLABSI) and surgical site infection (SSI) were the most common identified source for LOB. Presence of liver (OR: 2.66, p=0.035) and pelvic injury (OR: 2.25, p=0.038), gastrointestinal tract perforation (OR: 5.48, p=0.002), and massive transfusion (OR: 3.36, p=0.006) represented risk factors for bacteremia. Conclusions. Presence of pelvic and liver injury on arrival in emergency department, gastrointestinal tract perforation, and massive transfusion within the first 24 hours after trauma appears to be significant risk factors for bacteremia.

Crystalline polymers with functionalities along the backbone can store and transfer electrons, ions and gases and thus can be used in devices. However, the formation of such materials can be difficult. Here, Lee and others have produced highly crystalline conjugated polymers via two-monomer-connected precursors.